The discovery that 1,25-dihydroxy vitamin D is a major physiologically active form of the vitamin has stimulated interest in the synthesis of the vitamins and various analogs. Analogs are useful in studies of calcium metabolism and absorption and have potential clinical use in the treatment of disorders of calcium metabolism. When work in our group made proparglysilanes available as intermediates in organic synthesis, we undertook an examination of their applicability in the synthesis of vitamin D and its analogs. In the present proposal a lithiated propargylsilane would serve as the source of the diene system of vitamin D3 or its analogs. Following the stereospecific formation of the diene system, the lower ring A of the vitamin would be attached in a fashion which preserves the stereochemistry and regiochemistry present in an aliphatic precursor of the ring atoms. Resolved lithiated allene systems are expected to be prepared in the study. They are expected to be valuable agents for kinetic resolutions needed for total syntheses of vitamin D analogs and other natural products.